Many conventional oil wells include a rod string, which is reciprocated at surface by a pump jack to actuate a downhole pump.
Recently, rotary drive downhole pumps have been developed; these pumps find particular application in the production of crude oil laden with sand. A pump of this type is driven by a rotating drive string (such as a rod string or a tubular string), which is suspended in a stationary tubular production string.
There is a need for a rotary drive assembly which satisfactorily suspends the drive string and rotates it.
Such an assembly should be capable of permitting the drive string to be easily adjusted longitudinally, so that more or less drive string is in the wellbore. It should also preferably be adapted to permit of the use of an effective, conventional device, such as a stuffing box, to provide a seal around the drive string at the point where it protrudes from the upper end of the well's production string.